June 28, 2013
Metabolic Disorders May Be Triggered By Food Contaminants
April Flowers for redOrbit.com - Your Universe Online
Scientists suspect certain food contaminants of triggering, or worsening, metabolic disorders, especially when the contaminants accompany a high-fat diet.
A new study from the Inserm cardiovascular, metabolism, diabetology and nutrition unit used a mouse model that had been rendered obese with a high fat diet to study the effects of the food contaminants. The researchers introduced a "cocktail" of contaminants mixed with low doses of dioxin, PCB, bisphenol A and phtalates into the mouse diet.
The results of the study, published in the FASEB Journal, reveal metabolic changes occur in these mice, but that the effects differ depending on the gender. The scientists observed that female mice were more affected, with their obesity-induced glucose intolerance worsened and their estrogen pathway altered.
Because of metabolic complications such as diabetes and cardiovascular diseases, obesity has become a major public health problem. Genetic predispositions and lifestyle choices that combine overeating with a lack of exercise are the main causes. There is also a large body of evidence that suggests contaminants, particularly in food, are responsible for the obesity epidemic and the resulting metabolic changes.
For the current study, low doses of contaminants were added to the already high-fat diet being fed to the mouse model. The mother of this colony of mice was fed the same diet during gestation and lactation, and the mice were fed the same diet throughout their lives, creating a chronic exposure.
Four contaminants were added: two environmentally persistent contaminants (dioxin and PCB) and two non-persistent contaminants (phtalate and bisphenol A). Dioxin and PCB build up throughout the food chain through bioaccumulation, eventually ending up in our foods. On the other hand, phthalate and bisphenol A are omnipresent in our daily lives because of the intensive production of them, especially in the plastics industry. The dosages were low enough that they were not considered to have any health impacts on their own. These four contaminants were chosen because they are present in human food and because they are known to trigger endocrine disruption. A control group of mice was fed the same high-fat (obseogenic) diet without the added contaminants.
The research team ran glucose tolerance and insulin sensitivity tests on both groups, measuring for lipid accumulations in the liver and the expression of certain genes that play key roles in the metabolism of the adult mice. The effects of this diet are high dependent on the gender of the animal, according to the findings.
The addition of contaminants to the diet of females already on a high-fat diet, glucose intolerance worsened and the estrogen pathways were altered. In males, the addition of the contaminants changed the cholesterol and lipid metabolism. The team observed no change in weight between the mice with the contaminants added and the control group.
The team investigated the connection between the observed glucose intolerance and the alteration of the estrogen signaling for females exposed to the contaminants. Estrogen is known to protect against metabolic disorders, so the findings suggest in obese females, food contaminant exposure lowers this protection.
"With this study, we have succeeded in providing proof-of-concept that low doses of contaminants, even at levels normally considered to be without health impacts in humans, do in fact affect humans when subjected to chronic exposure, and when the contaminants are combined with a high-calorie diet," points out study author Brigitte Le Magueresse Battistoni.